Make tc-expr the same implementation as tc-expr/check.
Remove conditional tc-expr/check splits that no longer need to exist.
Remove tc-body, and 0 arg case in tc-body/check.
Remove tc/app/check.
Remove tc/lambda/check.
Improve filter simplification.

(T @ x) => (! S @ x) when their intersection is empty.
Rearrange how we look through filters in -and so this rule applies more.
Move tc-if merging results logic to tc-metafunctions for reuse.
Remove distinction between check and non check variant of check-subforms-unit.

Use new merge-tc-results as well.
This revealed some buggy tests as well which are also fixed.